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31.
The Systems Group at the Open University has always seen diagramming as an essential skill for students to learn and use properly if they are to become effective systems practitioners. However, teaching students at a distance to use diagramming effectively has posed challenges to both Lecturers and Students alike. While we have tried to provide some face-to-face opportunities to help teach this skill we have had to rely heavily on technological means most of the time. This paper reviews the role of diagramming in systems studies generally and specifically in Open University courses and assesses the advantages and disadvantages of the various technological methods used to teach diagramming over 30 years by the Systems Group. In so doing we try to determine how much the technology hinders or helps budding systems practitioners.  相似文献   
32.
Genes that mediate breast cancer metastasis to lung   总被引:1,自引:0,他引:1  
Minn AJ  Gupta GP  Siegel PM  Bos PD  Shu W  Giri DD  Viale A  Olshen AB  Gerald WL  Massagué J 《Nature》2005,436(7050):518-524
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33.
High plant diversity is needed to maintain ecosystem services   总被引:3,自引:0,他引:3  
Biodiversity is rapidly declining worldwide, and there is consensus that this can decrease ecosystem functioning and services. It remains unclear, though, whether few or many of the species in an ecosystem are needed to sustain the provisioning of ecosystem services. It has been hypothesized that most species would promote ecosystem services if many times, places, functions and environmental changes were considered; however, no previous study has considered all of these factors together. Here we show that 84% of the 147 grassland plant species studied in 17 biodiversity experiments promoted ecosystem functioning at least once. Different species promoted ecosystem functioning during different years, at different places, for different functions and under different environmental change scenarios. Furthermore, the species needed to provide one function during multiple years were not the same as those needed to provide multiple functions within one year. Our results indicate that even more species will be needed to maintain ecosystem functioning and services than previously suggested by studies that have either (1) considered only the number of species needed to promote one function under one set of environmental conditions, or (2) separately considered the importance of biodiversity for providing ecosystem functioning across multiple years, places, functions or environmental change scenarios. Therefore, although species may appear functionally redundant when one function is considered under one set of environmental conditions, many species are needed to maintain multiple functions at multiple times and places in a changing world.  相似文献   
34.
Although disk accretion onto compact objects-white dwarfs, neutron stars and black holes-is central to much of high-energy astrophysics, the mechanisms that enable this process have remained observationally difficult to determine. Accretion disks must transfer angular momentum in order for matter to travel radially inward onto the compact object. Internal viscosity from magnetic processes and disk winds can both in principle transfer angular momentum, but hitherto we lacked evidence that either occurs. Here we report that an X-ray-absorbing wind discovered in an observation of the stellar-mass black hole binary GRO J1655 - 40 (ref. 6) must be powered by a magnetic process that can also drive accretion through the disk. Detailed spectral analysis and modelling of the wind shows that it can only be powered by pressure generated by magnetic viscosity internal to the disk or magnetocentrifugal forces. This result demonstrates that disk accretion onto black holes is a fundamentally magnetic process.  相似文献   
35.
36.
    
IntroductionBeijing is the national capital of China,andthe capital of Beijing Municipality. The city islocated on the North China Plain,approximately1 50 km Northwest of the Bohai Sea at a north-latitude of40°.The municipality is approximately1 60 0 0 km2 in size,of which 2 / 3is mountainousarea encircling the western,northern and easternsides of the city. From the 1 990 census,the totalpopulation was 1 2 .9million,with 6. 4millionliving in urban areas,5.2 million living in the city,and …  相似文献   
37.
Insider action research describes the process when a member of an organisation undertakes an explicit action research role in addition to the normal functional roles they hold in an organisation. Real-world work-based research is relevant and important to many full-time managers, consultants and members of organisations including those who choose to undertake higher degrees in business as part-time postgraduate students. Within these programmes a proposal for an insider action research project is often associated with important and interesting research projects that have already arisen in an organisation where the researcher works full-time, and are part of their existing role and established working relationships with key stakeholders. Ethical issues in organisationally located insider action research can differ from other forms of action research because of role duality, i.e. that the researcher holds an ongoing work role and power relationships associated with this as well as the action research role. Ethical issues can be associated with choices about alternative options, expected impacts and outcomes on the researcher, participants, organisation and stakeholders, and these are important considerations for academic supervisors, institutional review boards and human research ethics committees.  相似文献   
38.
Srinivasan M  Ruina A 《Nature》2006,439(7072):72-75
Although people's legs are capable of a broad range of muscle-use and gait patterns, they generally prefer just two. They walk, swinging their body over a relatively straight leg with each step, or run, bouncing up off a bent leg between aerial phases. Walking feels easiest when going slowly, and running feels easiest when going faster. More unusual gaits seem more tiring. Perhaps this is because walking and running use the least energy. Addressing this classic conjecture with experiments requires comparing walking and running with many other strange and unpractised gaits. As an alternative, a basic understanding of gait choice might be obtained by calculating energy cost by using mechanics-based models. Here we use a minimal model that can describe walking and running as well as an infinite variety of other gaits. We use computer optimization to find which gaits are indeed energetically optimal for this model. At low speeds the optimization discovers the classic inverted-pendulum walk, at high speeds it discovers a bouncing run, even without springs, and at intermediate speeds it finds a new pendular-running gait that includes walking and running as extreme cases.  相似文献   
39.
The central theme of this paper is the current interest in most educational institutions in moving from teaching to learning as their main system model and the implications which technology media have for unravelling the debate and influencing the resulting practice (for example see Active Learning: Using the Internet for Teaching, Number 2, July, 1995), Our chosen strategy for dealing with the central theme is to consider how we use language, metaphor and models to describe systems for teaching and learning and what is the role of technology in these systems. In particular we describe how the Open University is moving from an analysis of individual technologies to a synthesis of the educational ideas into a sustainable system that conforms to the University's policy of supported open learning. This includes focusing on open and equal access to courses, considerable attention to staff development and training (specifically in core teaching areas such as face to face tuition, correspondence tuition, student support, telephone and other media supported communication) as well as the necessity and value of reflection on practice (e.g. see Baker, Tomlinson et al,, 1996). In this first section, taking as our starting point the traditional linear view of educational structures, we build upon the notion of the learning system and describe this as an approach with a somewhat long and surprising history originating in the Socratic method. An eductive, cyclic learning model is introduced, and the historical impact of technology on this model is briefly reviewed in a global context by addressing the specific issue of access from the developing countries. Following from this, in sections two and three two types of teaching are described, under the labels of conventional and distance. It is argued that each has strengths and tendencies towards the eductive learning system introduced in section one. However, it is also argued that each has flaws which provide problems for the development of a learning system which can be sustained at distance. An analysis based upon metaphor is applied. In section four, it is then argued that in the conventional model there is a system with excellent learning potential but with an organisational structure which often does not encourage it whereas in the distance model there is the potential organisation for providing feedback but often little effective use made of it. That lack of use includes the new technologies which are now being focused on by the Open University, both in terms of the INSTILL initiative (Integrate New Systems and Technologies Into Lifelong Learning) and the Technology Strategy for Academic Advantage (Laurillard, Christmas et al., 1996). These technologies are argued, in section five, to be capable of being tactically effective in stimulating and supporting the strategic aim of learning. Technology mediation is discussed both in terms of course-based teaching and in terms of research opportunities. In section six a range of problem/opportunity areas of immediate concern for the extension of this technologically mediated system to the developing countries are discussed, while policy implications for the extension of supported open learning are drawn out in section seven. These include policies toward co-learning, access to learning, quality standards and the authorship of educational material.  相似文献   
40.
The Office for National Statistics (ONS) has set up a project to investigate the feasibility of producing postcensal small area population estimates on a nationally consistent basis for England and Wales. Following on from earlier investigations to identify potential data sources and methods, ward and Super Output Area population estimates have been released as 'experimental statistics'. This article covers the methodology used to produce these estimates, feedback from user consultation with the initial estimates released at ward level, summary statistics on the population estimates for mid-2001 to mid-2003, and future developments for small area population estimates.  相似文献   
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